Process for the treatment of hides and skins with mucolytic enzymes



PROCESS FOR THE TREATMENT OF HIDES AND SKINS WITH MUCOLYTIC ENZYMES Donald Burton, Ronald Reed, and Frances Olga Flint, Leeds, England N Drawing. Application February 24, 1954 Serial No. 412,380

Claims priority,-application Great Britain February 26, 1953 a 9 Claims. (Cl. 195--8) This invention relates mainly to the treatment of hides and skins prior to tanning, or conversion into raw hide products, parchment, gelatine, glue and the like, but is also-concernedwith the treatment of tanned-hides and skins, and also with improvements in tanning liquors.

Mucoid materials or muco-polysaccharides are present in hides and skins. Such materials are essentially polymers of sugar-like compounds, usually, though not invariably, formed by .the linking together of simple sugars or amino-sugars with simple sugar acids, or with other, or the same,.sim'ple sugars so that long, chain-like molecules are formed. Such sugars include substituted and chemically modified sugars such as acetylated, methylated, sulphonated sugars and the like. The sugar acids and their compounds with alcohols are included as well I as their salts. Mucoid materials are therefore quite distinct from the proteins, which are essentially polymers of various types of amino acids. Mucoid materials are found .in close association with all the protein structures of hides and skins and the regions where they are present in rich amount include the epidermal-cerium junction, the elastic tissue fibers, the corium fibers and the spaces between these fibers.

The stability of the protein structures is determined by the mucoid materials in which they are embedded. If the mucoid materials are modified,.reduced in amount or removed entirely, the protein structures remaining are loosened and their cohesion is greatly modified.

An object of "the present invention is to provide an improved process for the depilation of hides and skins.

Another object of the invention is to provide a process for the treatment of hides and skins which enables hair, wool or other keratinous covering structures to be obtained in substantially undamaged condition and which is therefore of high quality.

Yet a further object of the invention is to provide an improved process for treating hides and skins to render them more suitable for tanning and other purposes.

Another object of'the invention is .to provide a skin or hide in which the grain surface or layer is very tight and smooth and free from distortion.

Yet another object-of the invention is to provide improved tanning liquors.

These and other objects are accomplished in accordance with the present invention which comprises subjecting fresh or salted ordry-salted or otherwise pre-.

served or treated hides and skins to the action of mucolytic enzymes.

In this specification and the following claims, mucolytic enzyme means any enzyme which, when used under the conditions of pH value and temperature appropriate to-it, will attackand/ordegrade'and/or digest mucoid materials or mmo-polysaccharides, which we have previously defined. These mucolytic enzymes include polygalacturonidase, pectinase, hyaluronidase, chondroitinase and amylase (sometimes also calleddiastase) andthe like. I

The treatment of-the hides or skins with mucolytic aten enzyme or enzymes can be carried out either at the covering structures, for the loosening of the fibrous structures of the cerium-or dermis of such hides and skins, and for hating them. It is possible to accomplish all these processes in one operation, but the operator-may wish, after soaking back orliming, or de-liming, or bating by practices already known to the art of leather 'making, to introduce the present process involving the action of mucolytic enzyme or mixture of mucolytic enzymes. Nor is it desired to restrict the use of the present process to operations before tanning, for its application is en'- visaged to tanned material and to material which has been dyed and/orfat-liquored and/ or finished. By hides and skins, there is also included woolskins e. g. sheep skins and fur-bearing skins-or pelts. Also pieces of'such hides and skinaincluding the tails of fur-bearing animals which may be used for the manufacture of paint and other types of brushesf By pieces of hides and skins, itis also meant to include pieces of limed or tanned hides and skins and any such trimmings which are normally used for themaking-of gelatine and glue; also included are pieces and trimmings of wool and fur-bearing skins and pelts, both in the tanned andun-tanned condition. By preserved or treated hides and skins is meant hides and skins at all stages of processing including the finished product.

The use of the presentprocess is meant to apply to all types of tannage and treatments used for the hides and skins, pieces, trimmings, etc. A

It is usual in depilation processes to adopt a process involving the use of lime and sulphide, such as sodium sulphide, for separation of the hair and epidermis from hides and skins,or to use proteolytic enzymes obtained from bacterial, mould, animal and plant sources. Such proteolytic enzymes bring about depilation by disrupting and/or digesting the essential protein structures of the epidermis and the epidermal-corium junction, but these proteolytic enzymes have no intrinsic action on the mucoid materials present in hides and skins.

It has now been found in accordance with this invention'that mucolytic enzymes, which do not attack and/ or digest the protein structures, but only the mucoid materials, are efiective in loosening the epidermal-corium junction of hides and skins and in detaching the epidermis and its elaborated structures such as hair, and sweat glands, entirely from the corium. The mucolytic enzymes attack themucoid material which is present at the epidermal junction and which embeds the protein structures at this junction.

Before subjecting the. hides and-skins to the action of mucolytic enzyme or mixture of mucolytic enzymesaccording to the present invention, it is possible, if so desired to soak them back according to the well established practices of the leather trade. hides and skins can be soaked in water with or without alkalis, wetting agents, bactericidal agents and similar reagents commonly "employed in soak'liqnors, withoutprejudice to the subsequent treatment with a mucolytic enzyme or mixture of mucolytio enzymes. Further, Without prejudice :to the subsequent mucolytic-treatment; the hides and skins may be-subjected to the mechanical opera-- tions of breaking, fleshing, and the like.

This prior treatment of conventional soaking the hidesv Thus, for 1 example the and skins, can be dispensed with as shall later be described. The soaked hides and skins are placed in a solution containing the mucolytic enzyme or mixture of mucolytic enzymes at a pH value appropriate to 'the particular enzyme or mixture of enzymes used. By solution at a pH value approprite to the particular enzyme or mixture of enzymes used, is meant a bufier solution, that is an aque ous solution which by its intrinsic chemical composition can maintain its pH value approximately constant and so is able to resist, or act as a buffer against, changes in its pH value when hydroxyl or hydrogen ions are added to it. In selecting such a buffer solution appropriate to the enzyme or mixture of enzymes used, the invention is not restricted to any one bufier solution for the carrying out of the process. However, it is advantageous When using a mucolytic enzyme or mixture of mucolytic enzymes to maintain the pH value of the solution approximately constant while subjecting the hides and skins to the action of the enzyme or enzymes.

It has been found, from experience, that the concentration of the mucolytic enzyme or mixture of mucolytic enzymes should generally be of the the order of 1% for the most beneficial results.

As a matter of expediency, it is found to be convenient to employtemperatures in the range 15 to 35 C. but it is to be understood that this is the preferred range of working and marginal variations at either end of this range may on occasion he used with advantage and are included within the scope of the invention. It is advantageous to maintain the temperature reasonably constant at the optimum value selected by the operator, throughout the duration of the treatment of the hides and skins. For cowhide, calf skin and woolskins, it is preferable for the best results to maintain the temperature of the buffer solution containing the enzyme or mixture of enzymes at about 30 C. throughout the treatment. For goat skins, it is preferred to maintain the temperature at about C.

throughout their treatment. It is to be understood however that the particular temperature used may be varied at the discretion of the operator who may wish to employ lower temperatures with a correspondingly longer time of treatment.

The hides and skins may be treated with the enzyme or enzymes under the conditions already described, in a drum, paddle or pit or vat or any suitable container, either with or without agitation, and/or aeration.

The hides and skins are treated with the enzyme or enzymes according to the conditions already described for periods ranging from 2 hours to 7 days or more. The period during which the hides and skins are subjected to the action of the enzyme or enzymes may be selected to fit in with the preferred cycle of daily operations, the type of hide or skin being treated and the particular bufi'er solution, enzyme or enzymes, and the temperature of working.

With certain hides and ,skins, and using a paddle or a drum, the hair and/or wool may be detached during the enzymatic treatment as a result of mechanical agitation or aeration. Alternatively, after the selected period of contact with the enzyme or enzymes solution, the hidesand skins may be withdrawn and unhaired or dewooled by practices normal in the leather and fellmongering trades. By these means, hair, wool, fur and other keratinous structures are obtained, together with pelt. The hair, wool, fur and other keratinous structures are of high. quality, in that these protein structures are undamaged by the action of the mucolytic enzyme or enzymes, and. only the material cementing these protein structures to the dermis or corium of the hide or skin has been loosened. and attacked by such enzymes. For these reasons, fibers of hair, wool, fur and other keratinous structures may be obtained which are of high quality and these hairs are generally longer than those obtained by existing methods, in that they still possess the entire original, natural length.

In the present method for the depilation of hides and skins as described above, buffer solution containing enzyme or mixture of enzymes is prepared by adding the enzyme or mixture of enzymes to the buffer solution before the hides and skins are introduced. It is not precluded, however, to add further amounts of enzyme or enzymes to the solution, while the hides and skins are being treated. Indeed, in most cases it is advantageous to add further quantities of enzyme or enzymes at appropriate intervals. during the treatment. I

in addition to using the mucolytic enzyme, or mixtureof mucolytic enzymes, in conjunction with bufier solutions as described previously, it is beneficial to includesimple salts of mineral acids such as sodium chloride,

sodium sulphate, potassium chloride in the solution used for treating the hides and skins. of such salts, added to the buffer solution in concentrations up to as much as 10% are beneficial for a number ot'reasons. Firstly, such salts control the degree ct swelling or plumpness of the hide or skin; secondly, they activate the enzyme or enzymes and so provide for more economical working; thirdly, they aid in the dispersion and solution of the cementing interfibrillary material loosened by the enzymatic action.

The mucolytic enzyme or enzymes in conjunction with buffer solutions and temperature control for the depilation of hides and skins may be used by a further method of working, which consists in allowing the hides and skins to remain in the enzyme solution made up as previously described for a suitable period of time, with or Without agitation of the system, then withdrawing the hides and skins so that the enzyme solution is retained by the hair, wool or fur and allowing the hides and skins to stand in piles, at'temperatures in the range 15 to 35 C. In the piles the hides and skins are stacked either flesh to flesh, or hair side to flesh or hair to hair. After standing in piles, the hides and skins may then be unhaired or dewooled according to known practices of the arts of leather making and fellmongering.

After preliminary treatment by the enzyme or enzymes as described above, the invention provides yet a further method of procedure in which the hides or skins may be hung in chambers or enclosed spaces maintained at a suitable temperature.

The invention also provides a method of dewooling sheep skins and dehairing hides and skins which comprises applying to the flesh side of the skins a paint composition comprising, a mucolytic enzyme or enzymes, a buffer solution of pH value appropriate to the enzyme or enzymes chosen, and salts such as sodium chloride, sodium sulphate, potassium sulphate, calcium chloride, etc. These components are mixed with a thickener, which may be flour (all types such as wheat, maize, barley, soya flour, etc.), starch, bran, gelatin, etc., so that a paste of the desired consistency is obtained; allowing the paint composition to remain on the piled or hung skins or hides for a suitable period of time and subsequently pulling the loosened wool or hair from the skins or hides.

In accordance with conventional methods for treating hides and skins preparatory to tanning, in addition to depilation, it is necessary to loosen the fibrous structures of the corium. This is generally accomplished by liming and by subsequent hating. According to the present invention, the fibrous structures can be loosened by the action of mucolytic enzymes. Although it is possible by the present invention to prepare hides and skins ready .for pickling and tanning, in one operational treatment with these enzymes, it is preferred that hides and skins unhaired or dewooled by existing practices be conveniently and rapidly loosened, in a preliminary treatment in preparation for tannage, by subjecting themto the action of mucolytic enzymes in the manner hereinbefore described.

Thus hides and skins which have been both unhaired or dewooled and partially loosened as a preparation Such salts, or mixturesfor tannage,.may befurther, prepared for tannage by batin-g? with mucolytic enzymes. I

By the. terms loosened and partially. loosened "is meantitheremoval'ofmore or lessv of the interfibrillary, mucoid cement material, ,in which the proteinlstructures of the hide orskinare embedded; In the prior art, this necessary operation Ofrenderingthe pelt structure more open is. termed loosening or openingup and is.accomplished.in the processof liming.

Further, even after preparation for tannage and subsequent tannage, by existing and conventional methods, the hides, skins, sides, pelts, etc., may withadvantage be treated with a mucolytic enzyme or mucolyticenzymes in the manner hereinbefore described- Tanned stock needs tobe. evenly loosened andopened up sothat the subsequentprocesses of dyeing, fat liquoring and finishing may be carried out evenly and satisfactorily. The treatment of tanned stock according to the invention.is particularly useful in the making of gloving and suede leather. A treatment of halfan hour, or longer according to the nature of the leather, with a mucolytic enzyme or enzymes, in the manner hereinbefore described, has been found to impart softness and suppleness to the tanned stock. Surprisingly the dyestuffs and fatvliquors as appliedin subsequent conventional operationsnow goon to the tanned stock so treated, much more evenly, so that more level shades of dyeing; can. be obtained. Certain dyestuffs are also found to penetrate the hide or skinfar more easily. This isof importance when light and. even pastel shades of dyed leather are required. and also in making of suede skins and sides, in that penetration of the dyestuif is muchgreater and more uniform.

It has now. been found that in treating: tanned stock with mucolytic enzymes in the manner hereinbefore described, it is. advantageousv to restrict thepH value of the enzymebath to a value within the range 3 to 8.

Treatment of tanned stock with mucolytic enzymes at pH values above 8 is. found to be impracticable in that stripping of tan may occur with vegetable-tanned leather and overneutralization with chromed leather. Hence the quality and value of the leather may be impaired. Also, it has been found impracticable to treat tanned stock with mucolytic enzymes below apI-ivalue of 3 in that either kind of leather may suffer. damage at pH values below 3. l

It is well known that unless the operation of liming is carried out carefully, a limed hide or pelt may manifest various degrees of fibre tightness. Thus the butt and neck regions may be quite tight, whilst the flanks may be quite loose. In the art of leather making, this phenomenon is termed irregular loosening? or opening up of the fibre structure of the hide or pelt, and it has been found to arise from the irregular removal of mucoid material from the hide or skin during liming. This uneven distribution of mucoid material, and hence degree of tightness or opening up of the fibre structures leads to irregular uptake of tans, dyestufis'and fat liquors. According tothe present invention, this uneveness or irregularity in fibre structure brought about by uneven liming can be corrected by treating the tanned stock with mucolytic enzymes, according to the manner hereinbefore described. Tanned stock, when treated according tothis invention, shows new properties in that any mucoid material remaining in association with the fibre structures is removed; thus the pelt structure becomes evenly loosened or opened up. This resulting evenness offibre structure is manifested by a regular-v degree of softness and suppleness over the pelt and by theeven or level uptake of dyestufis and fat liquors.

It is thus seen that the treatment with mucolytic enzymes can be applied at any stage'of the making of leather by existing conventional methods.

Further, the operation of soaking back is a well established practice in the leather trade and consists of treating the hides and skins with aqueous liquors with the objects of (1) restoring the hide or skin as nearly as possible to the condition it was in after flaying, (2) removing the salt from salted hides and skins and (3) wetting back the fibrous structures of the hides and skins by introducing water between them. The success of many of the subsequent operations in the preparation of hides and skins for tannage and other purposes depends on how well this soaking operation is carried out. Many of the difficulties associated with-soaking arise from the fact that the interfibrillary cement material becomes hardened around the fibers and hence makes the penetration of water a difiicult matter.

One of the objects of the present invention is to improve the soaking back operation on hides and skins by subjecting them to the action of a mucolytic enzyme or enzymes which can attack and loosen the mucoid components of the interfibrillary cement material.

This is-accomplished by subjecting the fresh or salted or dry-salted or dried or otherwise preserved or cured hides and skins to the action of mucolytic enzymes in substantially the same manneras hereinbefore described for the depliation of hides and skins by these enzymes. The fresh, or salted or dry-salted or dried or otherwise preserved or cured hides and skins are introduced into an aqueous buffer solution, of pH value appropriate to the mucolytic enzyme or enzymes selected, containing such enzyme or enzymes, and sodium chloride in concentrations ranging from 0 to 10%, at a temperature maintained within the range 15 to 35 C., for a suitable period of time. The penetration of the enzyme solution may be facilitated by the inclusion of a wetting agent in the solution or by previous treatment of the said hides or skins with a solution containing a wetting agent. After soaking back has been accomplished by this treatment, the operator can if it is desired, leave the hides or skins in the same aqueous buffer solution containing the hereinbefore mentioned components for a further period of time so that depilation, and/or loosening of the fibrous structures of the corium or-dermis, and/ or hating may be achieved, in the manner hereinbefore described. On the other hand, the operator may after soaking by the method of this invention, withdraw the hides and skins from the enzymatic solution and further treat them by conventional methods as used in the arts of leather making, fellmongering, raw hide, parchment, gelatin and allied trades.

In using the present compositions for soaking, depilation, bating and preparation for tannage, and in the treatment of hides and skins in any form hereinbefore mentioned, including tanned, dyed, fat liquored and finished products of hides and skins, it.has been found that the addition of certain substances, unless otherwise present due .to the intrinsic composition of the aqueous buffer solution, exert .an activatingefiect on the mucolytic enzyme or enzymes as employed according to the present invention, and hence make for the more economical .and improved application of such enzymes. Such activators include anions such as phosphate, citrate, formate, borate, iodide and sulfhydrate ions; metallic ions such as calcium, copper, zinc and chromium ions; hydrogen peroxide; simple sugars such as galactose, dextrose and maltose; disaccharides such as sucrose; starch, yeast, branand the various kinds offlour. These substances are effective in concentrations ranging from 1 to 5000 parts per 100,000 parts of the aforementioned bufier solution. The simple effect of the addition of such activators is to enhance the rate of removal of mucoid material from the hide or skin.

The pelt as obtained from the treatment of hides and skins with mucolytic enzymes, inaddition to being useful for the making of leather, can also be converted into other products. Thus another objective ofi the'invention is realized'in the production of new and improved rawhide goodsand parchments. In the prior art of making 7 raw-hide goods and parchments from hides and skins, it was generally accepted that liming (a treatment with aqueous liquors containing calcium hydroxide), is a necessary process. It has been found however that the pelt as obtained by the present invention which does not involve the use of lime liquors, is suitable for direct conversion into raw-hide goods and parchlnents. Further. in so far as the pelt produced according to the present invention is not at an approximately constant pH value as when the liming process is used, but can be produced over the wide range of pH values 3 to 12.5, new types of pelt are now available for conversion into raw-hide and parchment products.

Although the compositions for the treatment of hides and skins containing the mucolytic enzymes in accordance with the invention may be used over a wide range of pH 3 and pH 12.5, within this range and particularly when used with buffer compositions, it is preferred to carry out the treatment of the hides and skins at an intermediate pH of about pH 3 to pH 8.

A further object of the invention is the utilization of the pelt made as described by subjecting hides and skins, or pieces or trimmings of same, to the action of mucolytic enzymes, for the making of gelatin and glue products. It is well known that the properties of a gelatin depend on the pretreatment given to the pelt, and in the normal practice of making gelatin from hides and skins, it is usual to subject them to long periods of contact with lime liquors. The invention obviates the use of lime liquors and the pelt obtained by the present method is rapidly and easily convertible into gelatin by the conventional methods used in gelatin manufacture. Further, since the pelt can be obtained according to the invention over the entire range of pH values 3 to 12.5, hitherto unknown forms of gelatin, possessing characteristic properties, now become available.

A further object of the invention is concerned with improvements in vegetable tanning liquors. It is well known that myrobalans and some other vegetable tanning materials contain pectins and similar substances. These are wholly or partially extracted by water with the tannins and so are present in the resulting leach liquor 'or concentrated leach liquor, which is usually called an extract. It is also known that such extracts sometimes gel and even solidify during storage. It has been found that this gelation and solidification can be prevented by treatment of the leach liquor with a mu'colytic enzyme or a mixture of such enzymes. Further, the pectic substances are closely associated or combined with the tannins. Another object of this treatment is to break down these large complexes to give a liquor or extract which has modified tanning properties such as a mellower action on hides or skins. Yet a further object of this invention is the treatment of vegetable tanning liquors or extracts with a mucolytic enzyme or mixture of enzymes to modify their colors as, for example, to make them paler.

The following examples illustrate the invention with respect to presently preferred representative embodiments thereof; it will be understood that it is not intended to restrict the invention to these exemplary embodiments. In the said examples, parts by weight bear the same relation to parts by volume as dograms to milliliters. Percentages are by weight, and temperatures are in degrees Centigrade.

EXAMPLE 1 A dozen wet salted calfskins after being soaked, washed and fleshed, are introduced into the depilating bath made up in the following manner: 6800 parts by weight of sodium acetate crystals (CH COONa-3H O) are added to 5000 parts by volume of glacial acetic acid and diluted with water so that a buffer solution of about pH 4.0 is obtained. This bufier solution is diluted with water in this manner to make a total volume of 250,000 parts by volume. Common salt is added to give a final skins with the original depilating solution.

concentration thereof of 1%. 500 parts by weight of calcium pyrophosphate are added to provide a source of activating calcium and pyrophosphate ions. The temperature of the solution is brought to and maintained at 30. 2000 parts by weight of a pectinase preparation with bran as a carrier are added. The skins are allowed to remain in this depilating bath for 36 hours when the hair becomes loose. The skins are then withdrawn from the bath and unhaired by conventional methods. The pelts thus obtained are suitable either for liming or bating or pickling or tannage, or for conversion into parchment, gelatin or glue, by normal trade practices.

If in this example the sodium acetate is replaced by 1720 parts by weight of sodium formate and the glacial acetic acid by 5620 parts by weight of 90% formic acid, 250,000 parts by volume of a bufier solutionwith pH value of 3, may be obtained. 2500 parts by weight of common salt are added to give a final concentration of 1% together with 500'parts by weight of calcium pyrophosphate to provide a'source of activating calcium and pyrophosphate ions. This buffer solution is added to a bath containing pectinase as active ingredient.

EXAMPLE 2 Twelve wet salted calfskins similarly treated are placed in a depilating bath of exactly the same composition as described in Example 1 contained in a drum. The skins are drummed for 24 hours when the loosened hair has been removed by the mechanical action of the drum. The pelts thus obtained are suitable for liming, or conversion into parchment, or gelatin, or glue, or bating, or pickling, or tannage by normal trade practices.

Alternatively, twelve wet salted calfskins similarly treated are placed in a depilating bath of exactly the same composition as described above. The skins are paddled for six hours after which time they are drawn out and piled, hung or folded in a warm, humid atmosphere of a temperature within the range of 15 to 35 Any tendency to dry out is counteracted by damping the After 40 hours, the skins are unhaired by conventional methods.

EXAMPLE 3 One dozen wet salted domestic woolskins are soaked for 24 hours in water and are then transferred to an aqueous bath containing 0.5% of a non-ionic wetting agent which is an alkylphenylpolyglycolether at 30. After 2 hours contact with this wetting agent the woolskins are transferred to the depilating bath of exactly the same composition as described in Example 1 and contained in a wooden container with a loosely fitted lid;

the temperature being maintained at 30 throughout the Six wet salted domestic woolskins are soaked for 24 hours in water. They are then transferred to the depilating bath of substantially the same composition as described in Example 1 but containing in addition 0.5% of a non-ionic wetting agent which is an alkylphenylpolyglycolether. The skins are allowed to remain in this modified depilating bath for 24 hours, the temperature being maintained at 30 throughout the process. The skins are withdrawn and pulled to obtain the wool.

The pelts thus obtained are suitable for the same processes as previously mentioned.

EXAMPLE 5 One dozen wet salted domestic woolskins are soaked in water. for. 24 hours; They are then transferred to the modified depilating bath-containing 0.5%. of'a non-ionic wetting-1 agent which: is. an alkylphenylpolyglycolether in addition to the components already described. The skins are. allowed to remain. in. this depilating bath without agitation and at a temperature of 30for 2 hours. The skins are then withdrawn and piled, hung, folded or painted as described in the. next example, in a humid atmosphere of temperature Within the range of 15-35. Any. tendency to dry out iscounteracted by damping the skins with the original depilating solution. After 36 hours the skins are pulled and wool and pelt obtained.

EXAMPLE 6- Wet salted domestic woolskinsaresoak'ed in water for 24-11'0111'5 and then diained." They are then painted on the flesh side with a paint consisting of 50% wheat flour, 50% pectinase bran preparation mixedtoa suitable consistency with a buffer of pH 4.0'substantially the same as used-in the depilatingbath de'scribedin Example 1; The skinsare then piled 'flesh to' flesh; hung or folded in a humid atmosphere at a temperatureof 15 to35 After 48 hours the skins are pulled and wool and pelt obtained.

EXAMPLE '7' 12 fully chromed calf skins, prepared by conventional methods of leather manufacture in the blue condition and. damp, that is, in the condition immediately prior to the conventional practice of neutralization before dyeing are introduced into a bath of exactly the same composition Six fully chromed calfskins are treated in exactly the same manner as'described in Example 7, but after horsing up overnight are neutralized before dyeing.

EXAMPLE 9 g 6 calfskins. chrome tanned in a manner suitable for vegetable retannage are treated in exactly the same manner as described in Example 8. After horsing up overnight, these are treated with vegetable tanning extract containing myrobalans. After the completion of this combination tannage the skins are dyed according to normal practice. EXAMPLE 10 A wet salted calfskin after being soaked, washed and fleshed is introduced into'a depilating bath made up in the following manner: 115 parts by weight of borax and 300 parts by weight of boric acid are dissolved in a convenient amount of water so that a buffer solution of about pH 7.0 is obtained. The buffer solution is diluted with water to make a total volume of 20,000 parts by volume. Comrnon salt is added to give a final concentration of 2%.

The temperature ofthe solution is brought up to 30 when 100 parts by weight of'a powdered preparation of diastase is added.

The temperature is maintained at this value throughout the treatment and the skins arepaddled'for 20 hours. Theskin is then withdrawn from the'bath and uhaired by conventional methods.

EXAMPLE 11 Six squirrel tails in the partially or completely tanned condition, i. e. as:normally supplied to brush manufacturers by the fur trade, are soaked? overnight in cold water; They are then placediin adepilating bath of compositionrexactly similar to thatadescribed' in- Example 1 for thedepilation-of calfskins and-.contained;inan open Vessel of suitable size. T hetemperature:ismaintained at 10 35 and the treatment is allowed toproceed without agitation for. 40 hours.

The tails are then withdrawn from the bath, rinsed in water and partially dried-by hydroextraction. The fur from three of the squirrel tails is then pulled off in the manner normally, used in the brush making industry. The remaining three tails are dried out completely, stored for three weeks, wet back with .cold water, hydroextracted and the fur-fibers pulledoifin. the manner hereiubefore described.

EXAMPLE 12 A side of a sun dried Nigerian cowhide is placed in a soak liquor contained in an open soak pit and of exactly similar composition'to that described in Examplel for the depilation of calfskins. The temperature of the liquor is maintained at about 25 for 48 hours with occasional agitation by means of a wooden pole. After this time the hide is in a soaked condition and is then fleshed prior to depilation. A further addition of pectinase-bran preparation is then added to give a total concentration of approximately, 2%. The temperature is then brought to 30 and maintained there for a further 40 hours, again with occasional agitation by means of a wooden pole. The side is then withdrawn and depilated by a conventional method. The side is then suitable for either liming, bating or tanning by existing'methods.

EXAMPLE 14 A delimed calfskin in the condition normally encountered before hating by conventional treatment is placed in a paddle containing a'bating liquor of the same composition as in Example 1 for the depilation of calfskins. The temperature of the liquor is maintained at 35 for 3 hours and the skin is paddled continuously. After this treatment the skin issoft and porous. Similarly as with bated stock, the skin is ready for pickling or tanning by conventional methods.

EXAMPLE 15 A dried Australianwooled sheepskin is placed in a soak liquor contained in an open soak pit and of exactly similar composition to that described in EXampIe 3 for the dewooling of domestic sheepskins. The temperature of this static bath is maintained at 25 for 18 hours. The now soaked sheepskin is withdrawn and is suitable for subsequent treatment either by conventional methods or as hereinbefore described for domestic sheepskins.

EXAMPLE 16 75v parts by weight of a bran preparation of pectinase are extracted with 250 parts-by volume of water at 30. The solution of the enzymeis filtered and added to 3,000 parts by. volume of a myrobalans liquor of a specific gravity of 1.06. The resulting liquor is maintained at 30 for 36 hours. It is then concentrated by evaporation under reduced pressure to a specific gravity. of 1.2. The resulting extract is allowedto'stand for 3 months at temperatures ranging from 4 to 10. No gelation or solidification occurs.

EXAMPLE 17 5 parts by weight of a bran: preparation of pectinase are extracted with 20 parts by volume of water at 30. The filtered solution of .the enzyme1 is added to 200 parts by volume of a quebracho liquor of specific gravity of 1.06. The resulting liquor is maintained at 30 for 36 hours. As a control, parts by volume of water are added to 200 partsby volume of the quebracho liquor of specific gravity of 1.06. The control liquor is also maintained at 30 for 36 hours. Both liquors are diluted times and the color determined with a Lovibond Tintometer. The control gives the following figures:

Reds 3.8 Yellows 6.4

The treated liquoris obviously paler than the control and gives the results:

Reds 2.8 Yellows 4.5

EXAMPLE 18 Six wet-salted calfskins after being soaked, washed and fleshed, are introduced into a bath contained in a paddle and made up as follows:

100,000 parts by volume of water, 1,000 parts by weight of sodium chloride, 500 parts by weight of a bran preparation of pectinase.

The temperature of the bath is brought to and is maintained at this value. The skins are paddled in the bath for 30 hours, after which time the hair becomes loose. The skins are then withdrawn from the bath and unhaired by conventional methods. The pelts thus obtained are suitable either for liming, or bating, or pickling, or tannage, or for conversion into parchment, or gelatine or glue by normal trade practices.

EXAMPLE 19 Common salt is added to give a final concentration thereof of 1%. The temperature of the solution is brought to and maintained at 30 C. 2.4 kg. of diastase preparation are added. The skins are paddled in the bath for 3 hours, the temperature being maintained at 30 C.

After this treatment, the skins are withdrawn and horsed up overnight. They are then dyed according to normal practice.

In the foregoing examples, only buffer compositions of pH values 4, 7 and 10.4 have been specifically illustrated.

'It is clearly to be understood, however, that buffer compositions cover the range of pH values 3 to 12.5, as exemplified by:

pH ranged to 6 5,000 parts by volume of glacial acetic acid, are diluted with water and parts by weight of caustic soda flakes are added to this solution.

The buffer solution of pH value 3 so made, is diluted with water to make a total volume of 250,000 parts by volume.

By increasing the amount of caustic soda flakes from 50 parts by weight to 3,200 parts by weight, a bufler solution of pH value 6, is obtained. Bufler solutions with pH values between 3 and 6 can be obtained by adding caustic soda flakes within the range 50 to 3,200 parts by weight, to the above mentioned amount of glacial acetic acid.

pH range 5.8 to 8 1,700 parts by weight of potassium dihydrogen phos- 12 phate are dissolved in water and 37 parts by weight of caustic soda flakes are added to this solution. The buffer solution of pH'value 5.8 so made, is diluted with water to make a total volume of 250,000 parts by volume.

By increasing the amount of caustic soda flakes from 37 parts by weight to 470 parts by weight, a buffer solution of pH value 8 is obtained.

Buffer solutions with pH values between 5.8 and 8 can be obtained by adding caustic soda flakes within the range 37 to 470 parts by weight, to the above mentioned amount of potassium dihydrogen phosphate.

pH range 8 to 9.4

2,472 parts by Weight of boric acid are dissolved in water and 32 parts by weight of caustic soda flakes are added to this. The buffer solution of pH value 8.0 so made, is diluted with water to make a total volume of 250,000 parts by volume. By increasing the amount of caustic soda flake from 32 parts by weight to 250 parts by weight, a buffer solution of pH value 9.4 is obtained.

Buffer solutions with pH values between 8 and 9.4 can be obtained by adding caustic soda flakes within the range 32 to 250 parts by weight, to the above mentioned amount of boric acid.

pH range 8.45 to 12.5

1,500 parts by weight of glycine are dissolved in Water and 50 parts by weight of caustic soda flakes are added to this solution. The buffer solution of pH value 8.45 so made, is diluted with water to make a total volume of 250,000 parts by volume. By increasing the amount of causticsoda flakes from 50 parts by weight to 2,400 parts by weight a buffer solution of pH value 12.5 can be obtained. Buffer solutions with pH values between 8.45 and 12.5 can be obtained by adding caustic soda flakes Within the range 50 to 2,400 parts by weight to the above mentioned amount of glycine. Such buffer compositions may be substituted for the buffer compositions mentioned in the examples, with equally satisfactory results, always provided of course that the appropriate enzyme is used.

In the foregoing examples, the only activators mentioned by name consist of, sodium ions, calcium ions, pyrophosphate ions, wheat flour, iodide ions, potassium ions and borate ions. It is to be understood that any of the activators hereinbefore detailed, can be substituted for the activators mentioned in the examples, with equally satisfactory results. i

In the foregoing examples, only themucolytic enzymes, diastase and pectinase have been specifically illustrated. It is to be understood, however, that the other mucolytic enzymes hereinbefore referred to, can also be employed with satisfactory results, always provided of course the appropriate pH range is used.

In the foregoing examples, the proportions of mucolytic enzyme used cover the range 0.2% to 50%. It

is to be understood that this range may be extendedv within the limits 0.025%. to 50%. foregoing examples, the proportions of proteolytic enzymes cover the range 0.1% to 0.25%. Again it is clearly to be understood that the invention is applicable with concentrations of proteolytic enzyme ranging from 0.025% to 5%.

Of the mucolytic enzymes hereinbefore mentioned the use of pectinase for achieving the various objects of the invention is strongly favoured. The practical advantages of using pectinase as the mucolytic enzyme can be briefly summarised as follows:

It has optimum activity at a pH value of 4.0. The development of bacteria is greatly restricted at this value and hence any bacterial damage to the hide or skin is obviated. Further, in bringing about soaking, depilation, loosening and bating of the hide or skin at this pH value the pelts obtained by the present invention are in an ideal condition for tannage which, according to conven- Similarly, in the 13 tional methods, is usually commenced under acid conditions and at a pH value near to 4.

Thus the use of pectinase as the mucolytic enzyme leads in practice to a reduction of the number of handling operations and hence to greater economy. In the prior art hides and skins are mainly unhaired and loosened by lime liquors of pH value about 12.5. Before such limed stock can be tanned it is necessary to reduce the pH of the stock gradually by the separate operation of deliming and often complete the loosening by the further operation of hating. Also, in order to bring the stock into the correct condition for tannage a pickling operation is often employed.

By using pectinase as the mucolytic enzyme at pH values about 4 these separate operations are unnecessary.

A further advantage of using pectinase at pH values near 4 is that the hair, wool, fur and other keratinous structures of hides and skins can be obtained in substantially undamaged form. It is well known that hair, wool, fur and other keratinous structures are easily damaged by prolonged contact with alkaline solutions.

However, by bringing about depilation under the slightly acid conditions as hereinbefore specified when using pectinase according to our invention no damage to the hair, wool or fur can occur. Hence the use of pectinase leads to the preparation of high quality keratinous structures.

Whilst in the foregoing examples only a non-ionic wetting agent has been disclosed, it is to be understood that the invention will work satisfactorily with a cationic wetting agent as exemplified by cetyl pyridinium bromide, or with an anionic wetting agent as exemplified by the sodium salt of dodecyl benzene sulphonate.

Having thus disclosed the invention, what is claimed is:

1. A composition for the treatment of hides and flayed skins, comprising as the essential ingredient a mucolytic enzyme selected from the group consisting of polygalacturonidase, pectinase, hyaluronidase, chondroitinase and amylase in a concentration of 0.025 to 50%, which composition is bufiered in a pH range of 3 to 8 with 0.25 to 10% of buffer, said composition also containing an aqueous carrier.

2. A composition according to claim 1 in which the mucolytic enzyme is pectinase.

3. A composition according to claim 1 containing an alkylphenylpolyglycolether.

4. A composition according to claim 1 containing a simple salt of a mineral acid.

5. A composition according to claim 1 containing an anzyme activator.

6. A composition according to claim 4 in which the simple salt of a mineral acid is sodium chloride.

7. A process for the treatment of hides and flayed skins consisting essentially of applying to the latter a composition comprising as the essential ingredient a mucolytic enzyme selected from the group consisting of polygalacturonidase, pectinase, hyaluronidase, chondroitinase and amylase in a concentration of 0.025 to 50%, which composition is buffered in a pH range of 3 to 8 with 0.25 to 10% of a buffer, said composition also containing an aqueous carrier.

8. A process for the dehairing of hides and flayed skins comprising applying to the flesh side of the skins an aqueous composition containing as the essential ingredient a mucolytic enzyme selected from the group consisting of polygalacturonidase, pectinase, hyaluronidase, chon-droitinase and amylase in a concentration of 0.025 to 50%, which composition is bufiered in a pH range of 3 to 8 with 0.25 to 10% of buffer, and also containing a thickener selected from the group consisting of flour, starch and bran.

9. A tanning liquor comprising a mucolytic enzyme selected from the group consisting of polygalacturonidase, pectinase, hyaluronidase, chondroitinase and amylase in an aqueous extract buffered at pH 3 to 8, the concentration of the said enzyme being from about 0.025 to 10% and a bufler whose concentration is about 0.25 to 10%.

References Cited in the file of this patent UNITED STATES PATENTS 1,003,124 Rohm Sept. 12, 1911 1,444,250 Kern Feb. 6, 1923 1,820,957 Wallerstein Sept. 1, 1931 1,859,084 Gore May 17, 1932 1,967,679 Muench July 24, 1934 OTHER REFERENCES Sumner et al.: Enzymes, 1943, Academic Press, New York, page 87.

Lenker: Chemical Industries, XLVIII, March 1941, The Expanding Applications of Wetting Agents," pages 324 to 326.

McClean: Bioch. 1011111., vol. 35, part 1, 1941, pages 159183 (see, in particular, pages 162 and 172).

Porter: Bacterial Chemistry and Physiology, Wiley, 1946, pages 86-89.

Sumner et al.: Chemistry and Methods of Enzymes,

3rd ed., 1953, Academic Press, N. Y., pages 8, 21-23. 

1. A COMPOSITION FOR THE TREATMENT OF HIDES AMD FLAYED SKINS, COMPRISING AS THE ESSENTIAL INGREDIENT A MUCOLYTIC ENZYME SELECTED FROM THE GROUP CONSISTING OF POLYGALACTURONIDASE, PECTINASE, HYALURONIDASE, CHONDROITINASE AND AMYLASE IN A CONCENTRATION OF 0.025 TO 50%, WHICH COMPOSITION IS BUFFERED IN A PH RANGE OF 3 TO 8 WITH 0.25 TO 10% OF BUFFER, SAID COMPOSITION ALSO CONTAINING AN AQUEOUS CARRIER. 